Malaria transmission, primarily by the anopheline mosquitoes, remains a major source for human morbidity and mortality throughout the subtropical and tropical areas of the world. The long-term objectives of the proposed research are to identify, isolate, and characterize genes associated with the susceptibility and/or refractoriness of mosquito species to Plasmodium parasites, and to utilize this information to develop a malaria control strategy based on genetic disruption of mosquito vector competence. The objectives of this project are based on the general hypothesis that genes associated with Plasmodium refractoriness can be identified and isolated via determination of their genetic linkage associations with restriction fragment length polymorphism (RFLP) markers. The research described specifically examines the mosquito, Aedes aegypti, and its genetic relationship with the malarial parasite, Plasmodium gallinaceum, as a model system for elucidating genetic control mechanisms, because of the wealth of knowledge available concerning the genetics of this vector and the close phylogenetic relationship of this parasite with the major human malarial parasite, P. falciparum. The specific aims of this project are (1) to construct a saturated RFLP linkage map of A. aegypti, based on random cDNA sequences, (2) to identify linkage associations between these RFLP markers and the genes that confer Plasmodium refractoriness using interval or quantitative trait loci (QTL) mapping techniques, and (3) to begin efforts to isolate genes conferring Plasmodium refractoriness from a genome library of A. aegypti using chromosome walking techniques. These efforts, directed toward identification of the genes that define refractoriness or susceptibility in mosquito vectors responsible for malarial transmission, are clearly relevant to our understanding of the epidemiology of the disease and could identify novel mechanisms for disease prevention.